1. Field of the Invention
The present invention relates to a method of rolling steel sections, particularly in a universal section mill, wherein X-shape rolling and H-shape rolling are carried out alternatingly and specifically directed cooling of the steel section is carried out during rolling.
2. Description of the Related Art
Methods and rolling mills or rolling trains for rolling steel sections or girders are well known in the art, for example, from EP-A-0 256 409 and EP-B-0 498 733. When rolling steel sections, such as H-beams, U-beams and I-beams, significantly different temperature conditions occur over the cross-section due to the mass distribution at various intermediate cross-sections. During normal or forced cooling of the rolled girders to room temperature, these temperature differences produce stresses in the section which may result in distortions and/or curvatures which reduce the load-bearing capability of the girder. These temperature differences and the effects thereof are very difficult to eliminate in the finish-rolled girder and impair or may even make entirely impossible the cooling measures to be carried out for annealing from the rolling heat or for thermomechanical rolling.
Cooling devices used in the past are based on immersion cooling or spray cooling, as disclosed by "Stahl und Eisen" 109, (1989), No. 9, 10, pages 497 to 502, for a method of the above-described type. In the thermomechanical rolling process for heavy girder sections described in this reference, the method is composed of a combination of thermomechanical treatment and selective cooling of the flange/web connecting zone during rolling. The purpose of this is to achieve a uniform temperature distribution in the flange and, thus, to improve the homogeneity of the material properties over the product cross-section. It is attempted to spray the transition or connecting zone between flange and web either from the outside toward the flange side middles, or from the inside and outside. Both measures require extensive cooling stretches with adjustable nozzles. The cooling devices are either arranged between the roughing stands or following the finishing stands. In tandem reversing trains, the cooling devices are arranged on one side of the roll stands, so that the section or girder can be cooled during roughing rolling or after the finishing pass.